Method of connecting a new device to existing network

ABSTRACT

In a centralized radio network consisting of several devices one device acts as master or network coordinator and has a transmission range. Basically, other devices of the network are able to adopt the role of a coordinator. This ability is used to enlarge the area of the network to a size larger than the transmission range of the master. A device asks its parent PNC to become a child PNC when a newly turned on device acts as a temporary PNC and broadcasts an initiation beacon indicating that it looks for a child PNC. The child PNC reports that it is available. The new device determines one of the available child PNCs to be its new master. The acknowledgment for the selected child PNC may be broadcasted to inform all the devices in the transmission range of the new device. The new device quits the role of the temporary PNC and associates to the existing network.

The invention relates to a method of connecting a new device to anexisting network. The network or piconet comprises a coordinator whichcontrols a certain part, e.g. a cell or a cluster, of the network. Suchnetworks are often referred to as cluster-based or piconet-basednetworks. For example, the Bluetooth standard is used for piconet-basednetworks. The central controllers of the clusters are therefore calledCluster Heads or PicoNet Coordinators (PNCs). The inventive method isbased on a procedure of how a device that is out of the transmissionrange of an existing PNC can be informed about the existing PNC and howthe device then can be connected to the existing piconet therebyavoiding interference between neighbouring, uncoordinated piconets.

The invention especially relates to wireless personal area networks(WPAN) according to the protocol IEEE P802.15.3. This protocol is basedon a centralised and connection-oriented ad-hoc networking topology. Atinitialisation of a new network, one device or node will be required toassume the role of the coordinator of the WPAN, i.e. it will become thepiconet coordinator/scheduler (PNC). The PNC may

-   -   provide the basic network synchronisation timing,    -   perform admission control,    -   allocate network resources on the piconet according to a        pre-defined set of quality of service (QoS) polices,    -   allocate the amount of channel time (CT) resources available for        data transfer and    -   manage Power Safe requests.

A device that is trying to access the medium tries to detect acoordinator to associate to. If it does not detect a coordinator withina determined period of time it becomes itself a piconet coordinator. Adevice participating in one piconet sometimes looks for other piconetswith a better signal or a lower network load. Every device of a piconetcan hear the PNC and the slot assignments.

Overlapping cells that share the same channel frequency can build achild/neighbour piconet that timeshares a channel between two PNCs(parent and child/neighbour) sitting on the same frequency and beingwithin range.

The IEEE802.15.3 protocol may be used for a peer-to-peer communicationin a Wireless Personal Area Network (WPAN). The current medium accesscontrol (MAC) specification is based on a centralised approach. Accessto the wireless medium is granted by a central device called the piconetcoordinator (PNC). The PNC and all devices under its control form apiconet. It is possible that several piconets are formed in case not alldevices are located in mutual transmission and reception range. Onetopology defined in IEEE 802.15.3 for multiple piconet scenariosconsists of a hierarchy of PNCs. Per definition one PNC is the highestPNC in the hierarchy. This PNC can have one or several child-PNCs(CPNCs) which themselves can have several child-PNCs and so on. When adevice is turned on, it begins to scan all the available channels for anexisting PNC. While scanning, information about the channels in use isalso collected and stored. The devices use passive scanning, that islistening for beacon frames from PNC. This can be a good indication ofwhether or not there is a piconet in the vicinity. If during thescanning process a broadcast signal like a beacon has not been detected,the device assumes that there is not any PNC in its vicinity to which itcould associate. The device will then adopt the role of a PNC byinternally issuing a PNC start primitive.

Nishant Kumar, “802.15.3 MAC layer Overview and Proposed Enhancements toSupport UWB PHY”, Mobile and Portable Radio Research Group, VirginiaTech. discloses the feature child piconet. An alternate coordinatorrequests GTS (guaranteed time slots) using channel request time command.After receiving a GTS slot the child PNC starts sending beacon in theprivate GTS. A child piconet uses a distinct piconet ID(identification). The child piconet depends on the parent piconet onlyfor the allocation of a GTS. Association, authentication, security andacknowledgements are handled within the child piconet and do not involvethe parent PNC. A child PNC device can communicate with any member inthe parent piconet or the child piconet. Whereas a neighbour piconet isautonomous and relies on the parent piconet only for the GTS. It uses adistinct piconet ID. Association, authentication, security andacknowledgements are handled within a neighbour piconet and do notinvolve the parent PNC. A neighbour PNC device can only send channeltime requests to parent PNC and listen to its beacon.

A super frame consists of three subsections like beacon, CAP (contentionaccess period), CFP (Contention Free Period). The beacon transmitscontrol information, allocated GTS per stream index for the currentsuper frame and provides network wide timing information. The CAP usesCSMA/CA (Carrier Sense Medium Access with Collision Avoidance) withback-off procedure. It is used for seamless data transfer, channel timerequests, authentication, association request, response and othercommands in the system. The CRP (contention free period) comprisesoptional management time slots (MTS) and guaranteed time slots (GTS)that are used for asynchronous or isochronous data streams. The PNCcontrols in the CAP beacon the type of data to be sent during the CAP.

U.S. Pat. No. 6,381,467 B1 discloses an ad-hoc wireless network having aplurality of members with a master that while communicating on a firstcommunication channel recognises a need for assistance in managing thenetwork. In response to the need, the master negotiates with a member ofthe ad-hoc wireless network for the member to become a sub-master. Thesub-master then assumes management of a portion of the plurality ofmembers. The sub-master and the portion then communicate on a secondcommunication channel negotiated with the master. The processor isprogrammed to recognise the need for assistance in response to detectinga need to establish communications between a first communication devicein the ad-hoc wireless network and a second communication device withinrange of the first communication device but not within range of themaster. In this case, the master can negotiate this first communicationdevice for the first communication device to become a sub-master andthen to establish its own ad-hoc wireless network with the secondcommunication device on a communication channel different from thecommunication channel used by the master.

Godfrey Tan, “Interconnecting Bluetooth-like Personal Area Networks”, in1^(st) Annual Oxygen Workshop, Gloucester, Mass., 2001, discloses analgorithm for a personal area network that contracts a treeincrementally, one node at a time. When a node wishes to join thenetwork, it sends out frequent search announcements. Nodes that alreadybelong to the scatternet of multiple piconets periodically listen on apre-defined channel for these announcements and respond if they arewilling to accept a new neighbour. When there is more than one noderesponding to the new node, a decision has to be made on which presentnode a new device should join. This decision can be made by the new nodebased on the responses it hears or by the root. The root can gather theinformation from all the child nodes which hear the search messages andchoose which one to respond to the searching node. When a new nodeconnects to a node in the scatternet, the latter becomes a “parent” andthe former its “child”.

One object of the invention is to provide a method of connecting to anexisting centralized radio network (piconet) which comprises a masterdevice such as a network coordinator and at least one further device inthe transmission range of the network coordinator (PNC) a further devicenot being in the transmission range of the network coordinator. Afurther object is to provide a network to which a new device that is outof the transmission range of the network coordinator may associate to.

The object is solved by a method of connecting to an existingcentralized radio network (piconet) which comprises

-   -   a master device such as a network coordinator and    -   at least one further device in the transmission range of the        network coordinator        a at least one new device not being in the transmission range of        the network coordinator, with the method comprising the steps of    -   the new device becoming a temporary network coordinator which        broadcasts a beacon with an initiation request (such as a PNC        request IE) indicating that it intends to associate to an        existing network (piconet);    -   those devices that became a child network coordinator signalling        a response to the initiation beacon in form of one or several        broadcast or unicast frames indicating that they are available        child piconet coordinators;    -   the new device that acts as a temporary network coordinator        scanning the channels or frequencies, receiving the response        signals and choosing at least one of the available child network        coordinators as master;    -   acknowledging at least the selected child network coordinators'        response signals and    -   finishing the role of a temporary network coordinator and        becoming a slave with regard to the chosen child network        coordinator which works as a coordinator.

When the new device becomes a temporary PNC it is able to broadcastsignals such as beacons that are read by any device in the transmissionrange. Devices which are receiving the initiation beacon are informed ofthe new device's intention to associate to a network and at the sametime of the fact that it would not make sense to do a handover even ifthe signal level is higher than the one of its own PNC as the new devicewill not stay a PNC.

The step of becoming a child network coordinator is alternativelyperformed by a device that has received the beacon with the initiationrequest

-   -   asking its network coordinator (master) whether to become a        child network coordinator of the parent network coordinator in        order to become a master for the new device or    -   making itself a child network coordinator without asking the        parent network coordinator.

The initiation beacon may comprise an information element indicating atemporary network/piconet identification. This temporary identificationindicates that other devices neither should associate to the temporaryPNC nor do a handover.

The temporary network coordinator may wait for a response a certainperiod of time corresponding to a given number of beacon frames. Duringthat time the exchange between the network's coordinator and theprobable child PNC should be carried out. When that certain period oftime is over and scanning the channels/frequencies did not result indiscovering a child PNC, the new device itself becomes a new PNC andstarts an own piconet as there is not a piconet in the vicinity toassociate to.

According to one embodiment the acknowledgement of a selected childnetwork coordinator is transmitted as part of a beacon signal such thatother child PNCs which were available can be returned to their formerstate immediately.

The object is also solved by a centralized radio network (piconet)consisting of at least two devices wherein one of the at least twodevices is a network coordinator having a transmission range for itsbeacons and wherein at least one further device is in the transmissionrange of the network coordinator and wherein a new device scans thechannels or frequencies for discovering a network coordinator's beaconof an existing network in order to associate to it, wherein

-   -   the new device becomes a temporary network coordinator if it did        not receive a beacon signalled by a network coordinator within a        certain time and sends out an initiation beacon indicating that        it intends to associate to an existing network (piconet);    -   a device belonging to an existing network (piconet) that        receives the initiation beacon signal of the temporary network        coordinator asks its own network coordinator whether to become a        child network coordinator and in case of positive answer:        transmitting a corresponding response signal indicating that it        is an available child piconet coordinator to associate to;    -   the temporary network coordinator receives the response signals,        compares them and determines at least one of the available        devices which will become the child network coordinator (CPNC)        it associates itself to;    -   the temporary network coordinator (tempPNC) acknowledges the        availability signals of the selected CPNC(s) and changes its        state into being a slave with regard to the selected child        network coordinator(s) (CPNC(s)) and    -   the new device thus is connected to the existing network        (piconet).

A computer program that is run down by a processor and comprisesinstructions for the implementation of a method of connecting to anexisting network a new device.

A device of consumer electronics comprising a processor for running downa computer program that comprises instructions for the implementation ofa method of connecting to an existing network a new device that is outof the transmission range of the network coordinator and comprisingmeans for the implementation of such a method.

The invention may be summarized by a centralised radio networkconsisting of several devices wherein one device acts as master ornetwork coordinator and has a transmission range. Basically, otherdevices of the network are able to adopt the role of a coordinator. Thisability is used to enlarge the area of the network to a size larger thanthe transmission range of the master. A device asks its parent PNC tobecome a child PNC when a newly turned on device acts as a temporary PNCand broadcasts an initiation beacon indicating that it looks for a childPNC. The child PNC reports that it is available. The new devicedetermines one of the available child PNCs to be its new master. Theacknowledgment for the selected child PNC may be broadcasted to informall the devices in the transmission range of the new device. The newdevice quits the role of the temporary PNC and associates to theexisting network.

In the following, the invention will be described in further detail withreference to the accompanying drawing, wherein

FIG. 1 illustrates a situation according to the prior art with a deviceoutside the beacon transmission (Tx) range of a PNC-1 of a firstpiconet;

FIG. 2 illustrates one alternative of the invention with a topologyresulting in a single piconet where a new device is located outside thebeacon Tx range of the Parent PNC;

FIG. 3 illustrates another alternative of the invention with a topologywhere a device that has been turned on intends to associate a piconetand becomes a forwarding device;

FIG. 4 illustrates a further alternative of the invention where a changein the topology occurs resulting in two piconets with two PPNCs and withonly one CPNC and

FIG. 5 illustrates a situation where several CPNCs are available.

FIG. 6 is a flowchart illustrating steps of a method for connecting adevice to an existing centralized radio network (piconet).

FIG. 1 illustrates a situation according to the prior art with a deviceoutside the beacon transmission (Tx) range of a PNC-1 of a first piconetand thus not being able to associate to the first piconet. Thus, the newdevice itself has to become a PNC-2 and starts a second piconet. Twopiconets close to one another may result in interference. For example, adevice in the intersection of the transmission ranges of both PNCs mayswitch over to the other piconet if the beacon signal of that PNC is ofhigher strength. One solution to cope with the interference would be toopen the second piconet on a different channel. However, there aresystems like 802.15.3a, in which the channels are not fully orthogonalresulting in interference among the two piconets, even if they operateon two different channels.

FIG. 2 illustrates one alternative of the invention with a topologyresulting in a single piconet where a new device DEVnew, i.e. a devicethat has just been turned on, is located outside the beacon Tx range ofthe Parent PNC (PPNC), but within the hearing range of the Child PNC(CPNC). The new device associates itself to the CPNC which becomes itsmaster. By setting up a CPNC which becomes a master for a new device itis avoided that the new device outside the Tx range of a PNC itselfbecomes a PNC and starts a piconet on its own.

FIG. 3 illustrates another alternative of the invention with a topologywhere a device that has been turned on intends to associate to a piconetand becomes a forwarding device FDEV with two masters: the first masteris a CPNC-1 of a first piconet and the second master is a CPNC-2 of asecond piconet. In this example the former topology before theassociation of the new device is kept and the new device becomes a FDEV.By this process two completely isolated piconets are connected whilekeeping the current topology.

FIG. 4 illustrates a further alternative of the invention. Thearrangement of the devices is the same as the one of FIG. 3. But,according to the alternative a change in the topology occurs resultingin two piconets PN-5 and PN-6 with two PPNCs (PPNC-5 and PPNC-6) andwith only one CPNC-5 compared to FIG. 3 where the two piconets PN-3 andPN-4 comprise two PPNCs (PPNC-3 and PPNC-4) and two CPNCs (CPNC-3 andCPNC-4). The topology is changed after the association of the new deviceto the two piconets. In this example, when the new device associates tothe first piconet one device of the first piconet becomes a CPNC-5 forthe new device as well as for the former CPN-6 (s. FIG. 3) of the secondpiconet PN-6, the former CPN-6 becomes a FDEV associated to two masters,namely CPNC-5 and CPNC-6. By means of the newly formed CPNC-5 the twoformerly completely isolated piconets are connected with a change of thetopology.

FIG. 5 illustrates a situation where several CPNCs are available. Inthis example three piconets PN-7, PN-8, PN-9 exist, each of them with acertain transmission Tx range around the PPNC-7, PPNC-8, PPNC-9. Afurther device is turned on outside the transmission range of each ofthe PPNCs. The new device is located in such a way that in itstransmission range one device of each of the three piconets PN-7, PN-8,PN-9 exists. This means that three devices may be available as CPNC iftheir PPNC allows it. In this case, the new device which acts as atemporary PPNC when turned on, determines at least one of the availableCPNCs as its master. In most cases the new device will select exactlyone CPNC; however it might also be possible that the device wants toconnect to several piconets or to act as a forwarding device FDEVbetween the piconets, in which case it would select several CPNCs. Thesedevices will then be acknowledged as CPNC(s). After having determined atleast one of the available CPNCs as master the new device whichtemporarily acted as a PPNC returns to the behaviour of a slave. Theother available CPNCs which where not selected return to the state inwhich they previously were.

FIG. 6 is a flowchart illustrating steps of a method for connecting adevice to an existing centralized radio network (piconet).

At step 602, a new device to be added to the network becomes a temporarynetwork coordinator (tempPNC) which broadcasts a beacon with aninitiation request such as a PNC request IE in the beacon indicatingthat it intends to associate to an existing network (piconet).

At step 604, those devices that became a child network coordinator(CNPC) signalling a response to the initiation beacon in the form of oneor several broadcasts or unicast frames indicating that they areavailable child piconet coordinators (CNPCs)

At step 606, the new device to be added to the network acts as atemporary network coordinator (tempPNC) scanning the channels(frequencies), receiving the response signals and choosing at least oneof the available child network coordinators (CPNCs) as master

At step 608, the new device to be added to the network acknowledges atleast one of the selected child network coordinator's response signals.

At step 610, the new device to be added to the network terminates itsrole of acting as a temporary network coordinator (tempPNC) and becomesa slave with regard to the chosen child network coordinator (CPNC) thatworks as a coordinator.

1. A method of connecting a new device to be added to an existingcentralized radio network (piconet) the network comprising a masterdevice and at least one further device in the transmission range (Tx) ofthe network coordinator (PNC) at least one new device not being in thetransmission range (Tx) of the network coordinator (PNC), the methodcomprising the steps of: a) the new device to be added to the network,not being in the transmission range (Tx) of the network coordinator(PNC), becoming a temporary network coordinator (tempPNC) whichbroadcasts a beacon with an initiation request in the beacon indicatingthat it intends to associate to an existing network (piconet); b) adevice belonging to an existing network (piconet) that receives thebeacon with the initiation request of the temporary network coordinator(tempPNC) optionally asks its own network coordinator (PNC) whether tobecome a child network coordinator (CPNC) and in case of positive answeror in case the optional request at the own PNC is not needed:transmitting a corresponding response signal indicating that it is anavailable child piconet coordinator (CPNC) to associate to; c) thosedevices that became a child network coordinator (CPNC) signalling aresponse to the initiation beacon in form of one or several broadcast orunicast frames indicating that they are available child piconetcoordinators (CPNCs); d) the new device to be added to the networkacting as a temporary network coordinator (tempPNC) scanning thechannels or frequencies, receiving the response signals and choosing atleast one of the available child network coordinators (CPNCs) as master;e) the new device to be added to the network acknowledging at least oneof the selected child network coordinators' response signals and f) thenew device to be added to the network terminating its role of acting asa temporary network coordinator (tempPNC) and becoming a slave withregard to the chosen child network coordinator (CPNC) that works as acoordinator.
 2. A method as claimed in claim 1, wherein the step ofbecoming a child network coordinator (CPNC) is alternatively performedby a device that has received the beacon with the initiation request,the device receiving the beacon with the initiation request: a) the newdevice to be added asking its network coordinator (master) whether tobecome a child network coordinator (CPNC) of the parent networkcoordinator (PPNC) in order to become a master for the new device andthe PPNC giving a response to this request or otherwise, b) the newdevice to be added making itself a child network coordinator (CPNC)without asking the parent network coordinator (PPNC).
 3. A method asclaimed in claim 1, wherein the initiation beacon comprises aninformation element indicating a temporary network/piconetidentification (tempPNID).
 4. A method as claimed in claim 1, whereinthe temporary network coordinator (tempPNC) waits for a response acertain period of time corresponding to a given number of beacon frames.5. A method as claimed in claim 1, wherein the acknowledgement of aselected child network coordinator (CPNC) is transmitted as part of abeacon signal.
 6. A centralized radio network (piconet) consisting of atleast two devices wherein one of the at least two devices is a networkcoordinator (PNC) having a transmission range (Tx) for its beacons andwherein at least one further device is in the transmission range (Tx) ofthe network coordinator (PNC) and wherein: a new device desiring toconnect to an existing centralized radio network scans channels orfrequencies for discovering a network coordinator's beacon of anexisting network in order to associate to it, wherein the new devicebecomes a temporary network coordinator (tempPNC) if it did not receivea beacon signalled by a network coordinator's (PNC) beacon within acertain time and sends out an initiation beacon indicating that itintends to associate to an existing network (piconet); a devicebelonging to an existing network (piconet) that receives the initiationbeacon signal of the temporary network coordinator (tempPNC) optionallyasks its own network coordinator (PNC) whether to become a child networkcoordinator (CPNC) and in case of positive answer or in case theoptional request at the own PNC is not needed: transmitting acorresponding response signal indicating that it is an available childpiconet coordinator (CPNC) to associate to; the temporary networkcoordinator (tempPNC) receives the response signals, compares them anddetermines at least one of the available devices which will become thechild network coordinator (CPNC) it associates itself to; the temporarynetwork coordinator (tempPNC) acknowledges at least one of theavailability signals and changes its state into being a slave withregard to the selected child network coordinator(s) (CPNCs) and the newdevice thus is connected to the existing network (piconet).
 7. A methodaccording to claim 1, wherein the master device is a network coordinator(PNC).
 8. A method according to claim 1, wherein the initiation requestincluded in the broadcast beacon is a PNC request.
 9. A device to beconnected to an existing centralized radio network (piconet), thenetwork comprising a master device, at least one further device in thetransmission range (Tx) of the network coordinator (PNC) and said deviceto be connected to the existing centralized radio network (piconet),wherein said device to be connected is not in the transmission range(Tx) of the master device, the device to be connected to the existingnetwork including at least a processor configured for: a) enabling thedevice to become a temporary network coordinator (tempPNC) bybroadcasting a beacon with an initiation request, indicating that thedevice to be connected intends to associate to an existing network(piconet); b) enabling the device to scan channels (frequencies) astemporary network coordinator (tempPNC) to receive response signals tothe initiation beacon from those devices that became a child networkcoordinator (CNPC), the response signals indicating that the devicesthat became child network coordinators (CNPCs) are available as childpiconet coordinators (CPNCs); c) enabling the device to choose at leastone of the available child network coordinators (CPNCs) as master byacknowledging a corresponding response signal of the at least one of theavailable child network coordinator (CPNC); and d) enabling the deviceto cease acting in the capacity of temporary network coordinator(tempPNC) and instead become a slave to the chosen child networkcoordinator (CPNC).
 10. A device according to claim 9, wherein theresponse signals received from those devices that became a child networkcoordinator (CNPC) at said scanning step are in the form of one orseveral broadcasts or unicast frames indicating that the responding atleast one further device is available as a child piconet coordinator(CPNC).
 11. A device according to claim 9, wherein the master device isa network coordinator (PNC).
 12. A device according to claim 9, whereinthe initiation request included in the broadcast beacon is a PNCrequest.